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In Olympic swimming events, the winner is the first person to touch a pressure-sensitive wall at the end of the pool. How does this pad know that a person has touched it, rather than just registering the pressure of splashing water? If a swimmer just brushed it, would it fail to register their finish?I know that in the men's 100-metre butterfly event, the equipment was called into question when Michael Phelps of the US won his seventh gold medal of the games. How did officials know it had operated successfully?And finally, it's easy to judge the victor in a race taking place out of water - such as running - because a sensor beam can scan the finish line. But in the pool how can they ensure that all the wall pads are exactly in line at both ends of the pool? Are they aligned before water is added to the pool, and if so, how?Kelly Clitheroe, Grimsby, Lincolnshire, UK

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Answered by bks
on 2008-11-12 13:39:00

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Bela De Luna referring to the poster of the question and other respondents as idiots, is well out of order, and I'm not sure that saying the touch-pads don't 'feel' waves because they are a surface phenomenon, is actually correct.Perhaps Bela can tell us how far under the surface of the water a bow-wave no longer produces a force ahead of a moving object, or, indeed, how the Indonesian tsunami ever happened, if waves are only a surface manifestation in an otherwise static mass of water.Are the pads actually 'under water', or are they placed so that contact can be made above the surface, in case the swimmer's hands are partway through the stroke when contact is made?

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Asked by Michael Marshall
on 2009-07-08 17:01:09

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Answered by Michael Marshall
on 2009-07-08 16:01:54

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At the end of each lane there is a touch pad 90 centimetres high, 240 cm wide and 1 cm thick. Touching the pad stops the clock. Omega, the manufacturer of the touch pads used during the 2008 Olympics in Beijing, claimed that the pads react to the slightest touch from a swimmer#39;s hand, but not to the splashing of water.However, after the argument around Michael Phelps#39;s victory over Milorad Cavic in the 100 metres butterfly final at the games, later verified by digital images, it was revealed that a pressure of approximately 3 kilograms per square centimetre must be applied to the pad to activate it and stop the clock. Therefore, it can be said that the victor is the person who touches the pad with enough pressure and not necessarily the one who touches the pad first.Joanna Jastrzebska, North Shields, Tyne and Wear, UK

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Asked by Michael Marshall
on 2009-07-08 17:01:09

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Answered by Michael Marshall
on 2009-07-08 16:02:19

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The pressure pad#39;s tolerances are supposed to require a swimmer#39;s touch before it will trigger a response. A pulse of water would have to come from a high-power nozzle to apply enough pressure to trigger the pad.A swimmer approaching the end of a race cannot push a narrow enough or strong enough stream of water to trigger the pad. However, brushing the pad lightly may also not trigger it and so these days timing officials check overhead, high-speed cameras - like those used in track races - if the pad is just brushed or they are uncertain of the winner for any reason.Adrian Skinner, Bournemouth, Dorset, UK

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Asked by Michael Marshall
on 2009-07-08 17:01:09

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Answered by Michael Marshall
on 2009-07-08 16:02:47

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The pads are screw-fixed to the poolside along their top edge and in close contact with the poolside behind. The swimmer#39;s positive and forcible pressure on the pad must close any gap between the pad and the poolside, or it may not register.You have to hit the pad quite firmly to register, either at the turn or at the finish. Just occasionally the pad does indeed fail to register, either through poor swimmer contact or pad malfunction. This is why there are back-up timekeepers on each lane - both human and electronic - in order to verify a result. If a world or championship record is at stake, there must be at least three timekeepers present, and one of them has to be electronic.The final published time may have to be scrutinised by the referee if there has been a mechanical problem, sometimes a compromise or average time may be recorded at the referee#39;s discretion. Sometimes the record has to be disallowed if the electronic timing device is in any way compromised.If a pad should malfunction during the course of a race, it is removed and exchanged between events which takes about 5 minutes. The new pad is tested by punching it manually while timekeepers in a control room monitor the effect.In major events, reaction times off the starting blocks are also electronically measured by sensors and displayed instantly on the scoreboard (this identifies false starts) and the changeover time is also registered in relays, to show if the outgoing swimmer left the blocks before the incoming swimmer hit the pad. Relay swimmers still in the water while the race continues must take care not to touch any of the pads by mistake when they exit the pool, to avoid confusing the timing systems.Phil Sears, Amateur Swimming Association club coach, Dorking Swimming Club, Westcott, Surrey, UK

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Asked by Michael Marshall
on 2009-07-08 17:01:09

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Answered by Anonymous
on 2009-07-09 03:12:17

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The sensors are 1cm thick each? So a 100m pool is actually 99.98 metres? No wonder the records keep falling! ;-)

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Asked by Michael Marshall
on 2009-07-08 17:01:09

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Answered by James
on 2009-07-09 10:12:20

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the last cm is still swum, as the swimmer needs to close that gap in order to activate the sensor and complete the raceJames

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Asked by Michael Marshall
on 2009-07-08 17:01:09

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Answered by Anonymous
on 2009-07-11 01:30:29

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i do believe that rolex also sponsors phelps mmmmswim officials also want to promote (professional) swimming and breaking spitz#39;s record would help that mmmmm

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Asked by Michael Marshall
on 2009-07-08 17:01:09

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On the spike I was walking from Cowes on the Isle of Wight to Yarmouth along the coastal path in June. When nearing Yarmouth we saw this strange spike standing upright on a leaf (see photo). The top of the spike has broken off to the right.What created it? If it's of any use, the weather was warm.David Winstanley, Norwich, UK
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Answered by alex bennett
on 2009-07-09 12:20:23

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I#39;m the fist to comment but i think it#39;s was glue that set then the leaf was upside down then some how it came to what you can see now

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Asked by Michael Marshall
on 2009-07-08 17:00:23

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Categories: Plants, Unanswered.

Tags: animals, unanswered, domestic science, plants.

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On the spike I was walking from Cowes on the Isle of Wight to Yarmouth along the coastal path in June. When nearing Yarmouth we saw this strange spike standing upright on a leaf (see photo). The top of the spike has broken off to the right.What created it? If it's of any use, the weather was warm.David Winstanley, Norwich, UK
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Answered by Pat
on 2009-07-12 12:40:08

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The plant looks like a Pellitory (Parietaria sp) but I can#39;t see enough detail in the photo to have a clue what the spike is. I suspect it is unrelated to the plant it is on. Was the plant at ground level or up a wall? Not that I have anything in mind, just wondering as Pellitory of the Wall often is high on a wall.

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Asked by Michael Marshall
on 2009-07-08 17:00:23

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Categories: Plants, Unanswered.

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I can wiggle my ears, but only both at once, not one at a time. Why? I am fortunate enough to be able to wiggle my ears. However, I can only wiggle both at once, not one at a time. Why? Peter Slessenger, Reading, Berkshire, UK (Image: djeyewater, stock.xchng)
Editorial status: In magazine. (1 vote) average rating:3 There are 35 answer(s) for this question. View answers \| Submit an answer